Re: Colors -- What Am I Missing

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: dw85745 (dw85745_at_gbronline.com)
Date: 02/20/05 

Date: Sun, 20 Feb 2005 10:05:23 -0500

Thanks Mr Albers. Will check into it.

Made a quick example flipping the memory DC on top of a PBox.

With a pure white background the line shows up LtBlue.

HOWEVER with a multiple colored background, (used a "fall" leaf pattern of
greens and reds) the line shows up Black.

Still don't get it why the color change -- COPY_PEN should overwrite any
pixels on the bitmap (like SetPixel).

"Thorsten Albers" <albersRE@MOVEuni-freiburg.de> wrote in message
news:01c51751$52b1c8e0$088ee684@thaldesk...
> dw85745 <dw85745@gbronline.com> schrieb im Beitrag
> <oo-dnWNUVLZyMorfRVn-pg@gbronline.com>...
> > The problem I'm having is that once the lines are "initially" placed
they
> > become part of the bitmap.
>
> An IMHO good solution to this problem is the use of the Windows API
> procedure LineDDA(). This does not draw the Line itself but calculates the
> points of the line and reports them to Your application via a
LineDDAProc()
> callback procedure.
> In the callback procedure You may decide what to do with the data:
> a) You could read the current pixel color at the point, calculate the
color
> which would make the line at this point visible resp. invisible and then
> draw the pixel
> b) You could store all points in an array; the amount of data is even with
> a diagonal line not very high; to draw line: get the pixel to draw at a
> specific point from the array, store the current pixel color there to the
> array and draw the pixel; to erase the line: get the last pixel color fr a
> specific point from the array and draw the pixel.
>
> --
> ----------------------------------------------------------------------
> THORSTEN ALBERS Universität Freiburg
> albers@
> uni-freiburg.de
> ----------------------------------------------------------------------
>

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